From f340c0d1a3f40fdcba69cd291530a4debc58748f Mon Sep 17 00:00:00 2001
From: Ingo Molnar <mingo@elte.hu>
Date: Tue, 28 Jun 2005 16:40:42 +0200
Subject: [PATCH] [PATCH] Tweak idle thread setup semantics
This patch tweaks idle thread setup semantics a bit: instead of setting
NEED_RESCHED in init_idle(), we do an explicit schedule() before calling
into cpu_idle().
This patch, while having no negative side-effects, enables wider use of
cond_resched()s. (which might happen in the stock kernel too, but it's
particulary important for voluntary-preempt)
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
---
init/main.c | 7 +++++++
kernel/sched.c | 9 ++++++++-
2 files changed, 15 insertions(+), 1 deletion(-)
diff --git a/init/main.c b/init/main.c
index d324801729ba..b5e421e39ede 100644
--- a/init/main.c
+++ b/init/main.c
@@ -383,6 +383,13 @@ static void noinline rest_init(void)
numa_default_policy();
unlock_kernel();
preempt_enable_no_resched();
+
+ /*
+ * The boot idle thread must execute schedule()
+ * at least one to get things moving:
+ */
+ schedule();
+
cpu_idle();
}
diff --git a/kernel/sched.c b/kernel/sched.c
index e2b0d3e4dd06..5f2182d42241 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -4166,6 +4166,14 @@ void show_state(void)
read_unlock(&tasklist_lock);
}
+/**
+ * init_idle - set up an idle thread for a given CPU
+ * @idle: task in question
+ * @cpu: cpu the idle task belongs to
+ *
+ * NOTE: this function does not set the idle thread's NEED_RESCHED
+ * flag, to make booting more robust.
+ */
void __devinit init_idle(task_t *idle, int cpu)
{
runqueue_t *rq = cpu_rq(cpu);
@@ -4183,7 +4191,6 @@ void __devinit init_idle(task_t *idle, int cpu)
#if defined(CONFIG_SMP) && defined(__ARCH_WANT_UNLOCKED_CTXSW)
idle->oncpu = 1;
#endif
- set_tsk_need_resched(idle);
spin_unlock_irqrestore(&rq->lock, flags);
/* Set the preempt count _outside_ the spinlocks! */
--
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